I liked the original design but when I would try to push them in, I kept breaking them or they would keep breaking. I decided to use a bigger filament holder because some spools have a bigger hole in them. I decided to make these and a spool holder threaded. I use this stand with it. https://www.thingiverse.com/thing:2226146.
Here is the filament holder I use. It is threaded internally for these. https://www.thingiverse.com/thing:2935348
I used 50% due to it being made from PETG. I will test lower percentages with PLA soon.